Rigid vs collapsable lens focussing question

[giovatony]

I tried the Fed 50 collapsable on both my Zork 4 and Fed 2 and I can`t get the dual image to converge at infinity however close focus at 1 meter is fine or at least very close.

I had previously adjusted my fixed lenses for infinity and they do not seem to vary significantly when I switch.
Is this normal to have this difference in these two differently designed lenses? And how do I approach the remedy?
Thank you,
John

 

[giovatony]

I just discovered another potential problem. If the RF tab inside the lens mount sticks down a bit it can come into contact with the locking tab of a collapsable lens.
The tab on my Fed 2 is lower than the tab on the Z-4 thus making contact when I collapse the lens. I have to turn it slightly to bypass the RF tab that obstructs it.
Seems I will have to take my thumb and gently press the tab up towards the edge of the lens mount ring so those tabs on the lens clears. Is this advisable?

 

[Spyderman]

FED-2 are known to have the RF-sensor too low. It is often a problem with Jupiter-12 lenses.

Bending it slightly (1mm) upwards won't break anything... just do it. Then check with back removed and shutter open on B how it works.

 

[wolves3012]

I tried the Fed 50 collapsable on both my Zork 4 and Fed 2 and I can`t get the dual image to converge at infinity however close focus at 1 meter is fine or at least very close.

I had previously adjusted my fixed lenses for infinity and they do not seem to vary significantly when I switch.
Is this normal to have this difference in these two differently designed lenses? And how do I approach the remedy?
Thank you,
John

Collapsibles often won't work on a body that didn't come with one originally. Bodies using collapsible lenses have a thicker lens-mount flange to allow for the infinity-lock pin to depress as the lens is pushed to infinity. The cure, if you really want to use the lens, is to remove the infinity-lock pin. Other than that there's no issue.

On the FED 2, as spyderman says, you can bend the RF sensor arm up a fraction, it's common for them to be too low. Do it gently and only bend it a little, nothing should break. Check for correct working on the lens-cam afterwards - take the back off and see that the sensor still rides on the rotating lens cam.

 

[giovatony]

Many thanks to Spyderman and Wolves for their recommendations.
All appears to be well now poending a check re-calibration of the RF settings.
Again thanks.
John